1. Field of the Invention
The present invention relates to differential assemblies and, more particularly, to a differential case provided with lubrication passages for lubrication and cooling of pinion gears and the differential assembly.
2. Description of the Prior Art
Conventionally, differential assemblies well known in the prior art, are arranged in a power transmission system of a motor vehicle to allow a pair of output shafts operatively coupled to an input axle shaft to rotate at different speeds, thereby allowing vehicle wheels associated with each output axle shaft to maintain traction with the road while the vehicle is turning. Such a device essentially distributes the torque provided by the input shaft between the output axle shafts.
The typical automotive differential assembly is driven through a pinion shaft that is secured to a differential case. A plurality of pinion mate gears are mounted on the pinion shaft for rotation thereon. A spherical thrust washer adjacent to the differential case receives load from the pinion mate gear when the pinion mate gear rotates. The pinion mate gear rotates when there are different speeds between the driving axles as when cornering or when one wheel is on ice and is called differential action. When there is no differential action, the pinion mate gears do not rotate. The pinion mate gears drive side gears which are connected to the output axle shafts for driving the vehicle. Generally, the differential assembly is driven by a pinion on a propeller shaft which engages a ring gear on the differential case. As the differential case is rotated, the side gears are also rotated which in turn drives the output axle shafts for driving the vehicle. Generally this design of the differential assembly operates satisfactorily. However, one of the drawbacks of this design is when the spider gear rotates on the spider shaft at extreme speeds, due to a lack of sufficient lubrication, the excessive friction between the differential case and the pinion mate gear causes excessive wear and heat generation of a differential mechanism and occasional failure of the differential assembly.
Accordingly, it is the intent of this invention to overcome these shortcomings of the prior art.
The present invention provides an improved differential assembly having a differential case provided with lubrication passages for lubrication and cooling of pinion mate gears and the differential assembly.
The differential assembly in accordance with the preferred embodiment of the present invention includes the differential case rotatably supported within an axle housing and forming an inner cavity housing a differential gear mechanism rotatably supported in the differential case. The differential gear mechanism includes at least one pinion mate gear rotatably supported by a pinion shaft. The pinion shaft is secured to the differential case by extending through radial bores in the differential case. The pinion mate gear has a back face adapted to cooperate with a complementary pinion seat surface through a thrust washer disposed therebetween.
In order to provide efficient lubrication of the pinion mate gear, at least one lubrication passage is formed within the differential case adjacent to the radial bore receiving the pinion shaft. The lubrication passage provides fluid communication path for the lubricating oil from an oil reservoir in an axle housing to a space between the pinion seat surface of the differential case and the thrust washer of the pinion mate gear. The lubrication passage includes at least one inlet port provided on an outer peripheral surface of the differential case and spaced from the radial bore, and an outlet port open into the space between the pinion seat surface and the pinion mate gear and spaced from the radial bore.